Boot device error not accessible on Windows 10
If you receive errors INACCESSIBLE_BOOT_DEVICE after upgrading to Windows 10, or after using Reset in Windows 10, this message suggests a way to resolve the problem.
The INACCESSIBLE_BOOT_DEVICE error check usually indicates that the Windows operating system lost access to the system partition on boot. In this case, the system usually stops after a blue screen or stop error is displayed to protect against probable data damage or loss.
INACCESSIBLE DEVICE BOAT
Here are some suggestions you can try to solve the problem. See what applies in your case: